Piezoelectric Substrate Thickness Estimation via Interference Fringes
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Solution Overview
Problem
It is challenging to visually estimate the thickness tendency of a piezoelectric substrate, which is essential for achieving high-frequency elastic wave devices with precise thickness control.
Innovation Solution
A composite substrate is created by bonding a piezoelectric substrate with a predetermined fringe-shaped thickness distribution to a support substrate, allowing for visual estimation of thickness tendency through interference fringes formed when irradiated with monochromatic light, where the shape of intersections between bright and dark lines indicates thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion beam machining is performed to adjust thickness with high precision, then manufacturing precision is improved, but the ability to visually estimate thickness tendency is lost
Solution Approach 1:
The invention utilizes optical interference phenomena to produce color changes (interference fringes) on the piezoelectric substrate surface. When monochromatic light is irradiated, the reflected light creates bright and dark interference fringes that visually indicate thickness distribution. This allows operators to visually estimate thickness tendency without sacrificing the precision achieved through ion beam machining.
Solution Approach 2:
The invention introduces light as an intermediary to mediate between the thickness information and human observation. By using optical interference, the thickness distribution is translated into visible interference fringe patterns, serving as a mediator that conveys thickness information in a visually accessible form without altering the actual thickness precision.
2Speed
If the piezoelectric substrate is made thin (20 μm or less) for high-frequency operation, then device frequency capability is improved, but the difficulty of visually detecting thickness variations increases
Solution Approach 1:
The invention employs optical interference to convert minute thickness variations in thin substrates into visible color changes and interference fringe patterns. This amplification effect allows thickness variations in 20 μm or thinner substrates to be visually detected, overcoming the limitation of direct visual inspection for such thin materials used in high-frequency devices.
3Productivity
If a large diameter support substrate (2 inches or more) is used, then productivity is improved through larger processing area, but the complexity of visually estimating thickness tendency across the entire surface increases
Solution Approach 1:
The invention segments the thickness information into discrete interference fringe patterns that can be individually analyzed. By dividing the overall thickness distribution into observable fringe segments, operators can systematically estimate the overall thickness tendency across large substrate areas by analyzing the pattern of individual fringes rather than attempting to perceive the entire surface at once.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise visual estimation of the thickness tendency of the piezoelectric substrate, facilitating the use of the substrate in high-frequency elastic wave devices by correlating the pitch and amplitude of interference fringes with thickness variations.
Implementation Method 1
light reflected by a surface of the piezoelectric substrate and light reflected by a surface of the support substrate (a back surface of the piezoelectric substrate) interfere with each other
Implementation Method 2
when monochromatic light is applied, light reflected by a surface of the piezoelectric substrate and light reflected by a surface of the support substrate
Data Source
AI summary
A composite substrate according to the present invention includes a support substrate having a diameter of 2 inches or more, and a piezoelectric substrate having a thickness of 20 μm or less and bonded to the support substrate to transmit light. The piezoelectric substrate has a thickness distribution shaped like a fringe. A waveform having an amplitude within a range of 5 to 100 nm in a thickness direction and a pitch within a range of 0.5 to 20 mm in a width direction appears in the thickness distribution of the piezoelectric substrate in a cross section of the composite substrate taken along a line orthogonal to the fringe, and the pitch of the waveform correlates with a width of the fringe. In the piezoelectric substrate, the fringe may include either parallel fringes or spiral or concentric fringes.